Horvath S M, Agnew J W, Wagner J A, Bedi J F
Institute of Environmental Stress, University of California, Santa Barbara 93106.
Res Rep Health Eff Inst. 1988 Dec(21):1-21.
In order to assess the combined effects of altitude and acute carbon monoxide exposure, 11 male and 12 female subjects, nonsmokers in good health, were given incremental (two minutes at each workload) maximal aerobic capacity tests at four levels of ambient carbon monoxide (0, 50, 100, and 150 parts per million) at four altitudes (55, 1,524, 2,134, and 3,048 m). Five male and four female subjects completed all 16 experiments. The remaining subjects completed either eight or 12 experiments; at least eight male and eight female subjects were tested at each combination of carbon monoxide and altitude. Test conditions were double-blind. Subjects initially were screened with a medical history questionnaire, a 12-lead electrocardiogram, pulmonary function tests, anthropometric and body fat measurements, blood volume determinations, and a maximal aerobic capacity test. Each subject, after attaining the required altitude and ambient carbon monoxide level, performed the maximal aerobic capacity test (maximum VO2) meeting required conditions to assure that a maximal level was attained. Blood samples were drawn prior to the aerobic capacity test; at workloads of 50 watts, 100 watts, 150 watts, and maximum; at the fifth minute of recovery; and prior to repressurization to sea level. Blood was analyzed for hemoglobin, hematocrit, plasma proteins, lactates, and carboxyhemoglobin. Carbon-monoxide-carboxyhemoglobin uptake rates were derived from the submaximal workloads. Maximum VO2 was similar at 55 m and 1,524 m, and decreased from the 55-m value by 4 percent at 2,134 m and by 8 percent at 3,048 m. Despite increases in carboxyhemoglobin, no additional significant decreases in maximal aerobic capacity were observed. With increasing carbon monoxide, a decrease in maximum VO2 independent of altitude was observed. Carboxyhemoglobin concentrations at maximum VO2 were highest at 55 m and lowest at 3,048 m. Carboxyhemoglobin concentrations were lower in female subjects than in male subjects. Immediately prior to and at maximal workloads, carbon monoxide shifted into extravascular spaces and returned to the vascular space within five minutes after exercise stopped. We demonstrated that altitude hypoxia and carbon monoxide hypoxia act independently on the parameters of the maximal aerobic capacity test. We also demonstrated a decrease in the carbon monoxide concentration to carboxyhemoglobin as altitude increased, which can be attributed to the decrease in driving pressure of carbon monoxide at altitude.
为了评估海拔高度和急性一氧化碳暴露的联合影响，选取了11名男性和12名女性健康非吸烟者，在四个海拔高度（55米、1524米、2134米和3048米）的四个环境一氧化碳水平（百万分之0、50、100和150）下，进行递增式（每个工作量持续两分钟）最大有氧能力测试。5名男性和4名女性受试者完成了所有16项实验。其余受试者完成了8项或12项实验；在一氧化碳和海拔高度的每种组合下，至少有8名男性和8名女性受试者接受了测试。测试条件为双盲。受试者最初通过病史问卷、12导联心电图、肺功能测试、人体测量和体脂测量、血容量测定以及最大有氧能力测试进行筛选。每个受试者在达到所需海拔高度和环境一氧化碳水平后，进行符合要求条件的最大有氧能力测试（最大摄氧量），以确保达到最大水平。在有氧能力测试前、50瓦、100瓦、150瓦和最大工作量时、恢复的第5分钟以及重新加压到海平面之前采集血样。对血液进行血红蛋白、血细胞比容、血浆蛋白、乳酸和碳氧血红蛋白分析。一氧化碳-碳氧血红蛋白摄取率来自次最大工作量。55米和1524米处的最大摄氧量相似，在2134米处比55米处的值降低了4%，在3048米处降低了8%。尽管碳氧血红蛋白增加，但未观察到最大有氧能力有额外的显著下降。随着一氧化碳增加，观察到与海拔无关的最大摄氧量下降。最大摄氧量时的碳氧血红蛋白浓度在55米处最高，在3048米处最低。女性受试者的碳氧血红蛋白浓度低于男性受试者。在最大工作量之前和之时，一氧化碳转移到血管外空间，并在运动停止后五分钟内返回血管空间。我们证明了海拔缺氧和一氧化碳缺氧对最大有氧能力测试参数的作用是独立的。我们还证明了随着海拔升高，一氧化碳浓度向碳氧血红蛋白的转化减少，这可归因于海拔高度下一氧化碳驱动压力的降低。
